In this work the effect of tin-doped indium oxide (ITO) film thickness on the diffusion barrier between silicon and copper was studied. Four different Cu (100 nm)/ITO/Si samples with 10, 20,40 and 60 nm ITO were prepared by sputtering deposition. After annealing in a rapid thermal annealing furnace at various temperatures for 5 min, samples were characterized by four probe measurement for sheet resistance, X-ray diffraction analysis for phase identification, Scanning electron microscopy for surface morphology and transmission electron microscopy for microstructure. The results show that the ITO films of 20, 40 and 60 nm are good diffusion barriers between copper and silicon at least up to 700 degrees C and the failure temperature of samples with 20, 40 and 60 nm ITO is about 750 degrees C, which are 50 K higher than the sample with 10 run ITO. The failure of samples are chiefly due to the agglomeration of copper film. (c) 2006 Elsevier B.V All rights reserved.